Adsorption of CdSe Nanoparticles to Thiolated TiO2 Surfaces:  Influence of Intralayer Disulfide Formation on CdSe Surface Coverage

Jonathan R. Mann and David F. Watson*
Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260-3000
Langmuir, 2007, 23 (22), pp 10924–10928
DOI: 10.1021/la702127t
Publication Date (Web): September 19, 2007
Copyright © 2007 American Chemical Society

Abstract

Abstract Image

Mixed monolayers of hexadecanoic acid (HDA) and 16-mercaptohexadecanoic acid (MHDA) were adsorbed to nanocrystalline TiO2 films, and CdSe nanoparticles were attached to the mixed monolayer functionalized surfaces. IR absorption spectroscopy was used to characterize the equilibrium binding of HDA and MHDA to TiO2. Surface adduct formation constants (Kad) of (4 ± 2) × 103 M-1 and (6 ± 4) × 103 M-1 were measured for HDA and MHDA, respectively. CdSe nanoparticles were adsorbed to the terminal thiol groups of MHDA. The surface coverage of CdSe was greater on mixed monolayers, consisting of approximately 12% MHDA and 88% HDA, than on pure MHDA monolayers. A mechanism is proposed wherein intralayer disulfide formation between MHDA thiol groups causes decreased reactivity toward CdSe nanoparticles. Disulfide formation is less significant at low fractional surface coverages of MHDA. The mechanism is supported by an increase of CdSe adsorption upon chemical reduction of surface disulfides to thiols. Our findings highlight the effect of intermolecular interactions on the affinity of nanoparticles for monolayer-functionalized surfaces.

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History

  • Published In Issue October 23, 2007
  • Received July 16, 2007
    Revised September 4, 2007

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